Beijing University of TechnologyBeijing
Beijing University of TechnologyBeijing
Liu J.,Beijing University of TechnologyBeijing |
Lai Y.,Beijing University of TechnologyBeijing |
Diao Z.,Beijing University of TechnologyBeijing |
Chen Y.,Arizona State University
Simulation Modelling Practice and Theory | Year: 2017
In software-defined networks (SDN), most controllers do not have an established control function for endpoint users and access terminals to access network, which may lead to many attacks. In order to address the problem of security check on access terminals, a secure trusted access method in SDN is designed and implemented in this paper. The method includes an access architecture design and a security access authentication protocol. The access architecture combines the characteristics of the trusted access technology and SDN architecture, and enhances the access security of SDN. The security access authentication protocol specifies the specific structure and implementation of data exchange in the access process. The architecture and protocol implemented in this paper can complete the credibility judgment of the access device and user's identification. Furthermore, it provides different trusted users with different network access permissions. Experiments show that the proposed access method is more secure than the access method that is based on IP address, MAC address and user identity authentication only, thus can effectively guarantee the access security of SDN. © 2017 Elsevier B.V.
Ma Y.,Xiamen University |
Xie Q.,Xiamen University |
Liu X.,Xiamen University |
Zhao Y.,Xiamen University |
And 4 more authors.
Electrochimica Acta | Year: 2015
Amorphous ZnSnO3 double-shell and yolk-shell hollow microcubes were synthesized by calcination of their corresponding ZnSn(OH)6 precursors pre-prepared through a facile chemical solution method in argon. The as-prepared amorphous ZnSnO3 double-shell hollow microcubes have an average edge length of 1.6 μm. When used as the anode materials, amorphous ZnSnO3 double-shell hollow microcubes (D-ZnSnO3) reveal better electrochemical properties than ZnSnO3 yolk-shell counterparts (Y-ZnSnO3). D-ZnSnO3 anodes can retain a high reversible capacity of 741 mA h g-1 after 50 cycles with a coulombic efficiency of 99% at 100 mA g-1. The amorphous feature and unique box-in-box hollow architecture of D-ZnSnO3 play a key role in their excellent electrochemical properties. © 2015 Published by Elsevier Ltd.
Wu Y.-T.,Beijing University of TechnologyBeijing |
Liu S.-W.,Beijing University of TechnologyBeijing |
Xiong Y.-X.,Beijing University of Civil Engineering and Architecture |
Ma C.-F.,Beijing University of TechnologyBeijing |
Ding Y.-L.,University of Birmingham
Applied Thermal Engineering | Year: 2015
Abstract An experimental system of parabolic trough solar collector and heat transfer was set up with a new molten salt employed as the heat transfer medium (with a melting point of 86 C and a working temperature upper limit of 550 C). The circulation of molten salts in the system took place over 1000 h. Experiments were conducted to obtain the heat loss of the Heat Collector Element (HCE), the total heat transfer coefficient of the water-to-salt heat exchanger, and the convective heat transfer coefficients for the low melting point molten salt in a circular tube. The results show that the thermal loss of the tested HCE is higher than that of the PTR70, and the thermal loss at the joints of the collector tube represents about 5% of the total loss in the entire tube. The total heat transfer coefficient of the water-to-salt heat exchanger was between 600 and 1200 W/(m2·k) in the ranges of 10,000 < Re < 21,000 and 9.5 < Pr < 12.2. The experimental data show good agreement with existing well-known correlations presented by the Sieder-Tate equation and the Gnielinski equation. This experimental study on heat loss from molten salt flow in a receiver tube will hopefully serve as a helpful reference for applications in parabolic trough systems. © 2015 Elsevier Ltd.
Wei Z.,Wuhan University |
Wei Z.,Beijing University of TechnologyBeijing |
Wei Z.,University of Oxford |
Sprott J.C.,University of Wisconsin - Madison |
Chen H.,Wuhan University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2015
Abstract This paper describes a class of third-order explicit autonomous differential equations, called jerk equations, with quadratic nonlinearities that can generate a catalog of nine elementary dissipative chaotic flows with the unusual feature of having a single non-hyperbolic equilibrium. They represent an interesting sub-class of dynamical systems that can exhibit many major features of regular and chaotic motion. The proposed systems are investigated through numerical simulations and theoretical analysis. For these jerk dynamical systems, a certain amount of nonlinearity is sufficient to produce chaos through a sequence of period-doubling bifurcations. © 2015 Elsevier B.V.
Zhang M.,Texas A&M University |
Lu W.,Texas A&M University |
Li J.-R.,Texas A&M University |
Li J.-R.,Beijing University of TechnologyBeijing |
And 5 more authors.
Inorganic Chemistry Frontiers | Year: 2014
Two nucleobase-incorporated metal-organic materials were designed, synthesized and structurally characterized. PCN-530 is among the few examples of metal-organic frameworks that utilize adenine as a constructional unit, while TMOP-1 is the first existing example of a crystallographically characterized nucleobase-incorporated metal-organic polyhedron. This work also offers a general perspective for the design and synthesis of nucleobase-incorporated metal-organic materials. This journal is © The Royal Society of Chemistry.
Ma H.,Beijing Research Institute of Uranium Geology |
Yin L.,Ecole Polytechnique Federale de Lausanne |
Gong Q.,Beijing University of TechnologyBeijing |
Wang J.,Beijing Research Institute of Uranium Geology
International Journal of Mining Science and Technology | Year: 2015
Abstract Mixed-face ground encountered in Tunnel Boring Machine (TBM) tunneling presents great challenges and may trigger potential hazards without warning. A detailed understanding of such unfavorable conditions is therefore critical to a successful bored tunnel. In this paper, we firstly present a brief review of the definition, classification and the factors related to mixed-face conditions. Secondly, for a better understanding of this topic, we investigate the main difficulties and problems involved in TBM tunnelling under mixed-face ground with detailed cases. Thirdly, from the viewpoint of rock-machine interaction, we give some suggestions on the corresponding mitigation measurements from three categories: (i) selection of TBM type and modification of TBM, (ii) condition of ground and (iii) optimization of TBM operation. © 2015 Published by Elsevier B.V. on behalf of China University of Mining & Technology.
Wu S.,China Household Electrical Appliance Research InstituteBeijing |
Li H.,Beijing University of TechnologyBeijing |
Cheng J.,China National Institute of StandardizationBeijing |
Tian C.,Beijing University of TechnologyBeijing
Applied Thermal Engineering | Year: 2013
The promotion of Energy Efficiency Standards and the implementation of Energy Labels have greatly improved energy efficiencies of Chinese refrigeration products in recent years. These products are now moving towards multiple heat sources and multiple functions, to obtain further energy-savings. Some typical products, such as solar energy refrigerators and air conditioning-water heater system are introduced. The current energy efficiencies of Chinese refrigeration products are also introduced in this paper. Some recommendations are given to make the standards accommodate these changes. © 2012 Published by Elsevier Ltd.
Ding D.-W.,University of Science and Technology of China |
Wang H.,Beijing University of TechnologyBeijing |
Li X.,University of Science and Technology of China
Systems and Control Letters | Year: 2015
Abstract This paper addresses the problem of H-/H∞ fault detection for two-dimensional (2-D) systems with disturbances in Roesser model. A fault detection observer is designed to satisfy a finite frequency H- index and an H∞ index simultaneously. The finite frequency H- index is used to increase the fault sensitivity in low frequency domain while the H∞ index is used to attenuate the effects of disturbances in full frequency domain. By the generalized Kalman-Yakubovich-Popov lemma and some useful lemmas, sufficient design conditions are obtained. An example is given to illustrate the effectiveness of the proposed method. © 2015 Elsevier B.V.
Xia G.D.,Beijing University of TechnologyBeijing |
Ma D.D.,Beijing University of TechnologyBeijing |
Wang W.,Beijing University of TechnologyBeijing |
Zhai Y.L.,Beijing University of TechnologyBeijing
International Journal of Heat and Mass Transfer | Year: 2015
3D-IC is getting increasingly attractive, as it improves speed and frequency and reduces power consumption, noise and latency. However, three-dimension (3D) integration technology brings a new serious challenge to chip thermal management with the power density increased exponentially. Interlayer micro-channel liquid cooling is a promising and scalable solution for high heat flux removal in 3D-IC. The effects of geometric parameters on fluid flow and heat transfer characteristics in interlayer micro-channel cooling for 3D-IC with triangular reentrant cavities (TRC) and fan-shaped reentrant cavities (FRC) are numerically investigated. 3D-IC with TRC and FRC for pitch = 0.1/0.2 mm and height = 0.2 mm are analyzed and compared with rectangular micro-channel (RMC) for 1 cm2 heat areas. Results show that the heat rate and pressure drop distributions of each layer for length = 5 mm and pitch = 0.2 mm are more uniform. The micro-channels of pitch = 0.1 mm have better heat transfer performance, simultaneously cause the pressure drop and pumping power increasing sharply, which are undesirable and uneconomical for 3D-IC. For smaller Re, the micro-channels with surface enhancement structures TRC and FRC deteriorate heat transfer. While at the larger Re, heat transfer is enhanced, which can be attributed to heat transfer area increased, boundary layer thinned, boundary layer interrupted and chaotic advection by generating vortices. The 3D-IC with FRC-L5-P0.2 has better heat transfer performance and lowest pumping power, which is more suitable and economical for 3D-IC inter-layer cooling. For channel length of 10 mm, the fluid temperature is higher in the last 5 mm, which deteriorates heat transfer effect, simultaneously the longer length leads to pumping power and flow resistance enlarged. Besides, 3D-IC with FRC decreases the laminar stagnation zones and improves the heat transfer performance, due to owning bigger included angle of the expansion and constriction walls in channel. © 2015 Elsevier Ltd.
Zhai Y.L.,Beijing University of TechnologyBeijing |
Xia G.D.,Beijing University of TechnologyBeijing |
Liu X.F.,Beijing University of TechnologyBeijing |
Wang J.,Beijing University of TechnologyBeijing
Energy Conversion and Management | Year: 2015
A new type of double-layered micro heat sink (DL-MCHS) with complex structure is designed and investigated numerically. Moreover, a model of entropy generation rate of DL-MCHSs is also derived from the first and second laws of thermodynamics. Results for the relationship of entropy generation rate between the first and second layer of DL-MCHSs, total entropy generation rate, the average temperature on the bottom wall, thermal resistance and pressure drop are investigated in detail, respectively. The results indicate that the effect of entropy generation rate of the first layer on total entropy generation rate is dominant. The thermal characteristic of DL-MCHSs with complex structure is better than that of all DL-MCHSs and single-layered micro heat sinks (SL-MCHSs) with simple structure under the same volumetric flow rate. However, DL-MCHSs only show better thermodynamic advantage and thermal performance than SL-MCHSs with complex structure when the volumetric flow rate larger than a certain value. It is not reasonable to use DL-MCHSs for cooling microelectronic equipments under small volumetric flow rate due to the larger irreversibility. Finally, the pressure drop of DL-MHCSs can be reduced by properly changing the channel height under various volumetric flow rates. Due to the less irreversibility and more uniform temperature distribution on the bottom wall, DL-MCHSs can effectively eliminate the internal thermal stresses in microelectronic equipments. Therefore, DL-MCHSs are an alternative method for the electronic cooling. Moreover, the thermodynamic analysis provides references for the actual application design. © 2015 Elsevier Ltd.